Sewing machine power transmission system



May 31, 1966 P. E. MYERS 3,253,563

SEWING MACHINE POWER TRANSMISSION SYSTEM May 31, 1966 P. E. MYERS 3,253,563

SEWING MACHINE POWER TRANSMISSION SYSTEM Filed Feb. 2l, 1964 5 Sheets-Sheet 2 Si llllHlllHlI I l I l 2 mlm wh" .HIW'IH l 2% w MQW May 31, 1966 P. E. MYERS SEWING MACHINE POWER TRANSMISSON SYS-TEM 5 Sheets-Sheet 5 Filed Feb. 2l, 1964 INVENTOR. ///P MYERS P. E. MYERS SEWING MACHINE POWER TRANSMISSION SYSTEM May 31,1966

May 31, 1966 P. E. MYERS SEWING MACHINE POWER TRANSMISSION SYSTEM 5 Sheets-Sheet 5 Filed Feb. 2l, 1964 INVENTOR. ffm/ i fus/fw, BY f M] MJ, QM

United States Patent() 3,253,563 SEWING MACHINE POWER TRANSMISSION SYSTEM Philip E. Myers, Beloit, Wis., assignor to Warner Electric Brake 8; Clutch Company, South Beloit, Ill.,'a corporation of Delaware Filed Feb. 21, 1964, Ser. No. 346,510 14 Claims. (Cl. 112-220) The present invention relates in general to a power transmission system for sewing machines and, more particularly, to an improved drive arrangement for sewing machines of the type employing electromagnetic power transmitters. In its principal aspects, the invention is concerned with an improved sewing machine power transmission system which permits of automatic operation at relatively constant selectable speeds and, more specifically, at a .selectable one of two or more substantially constant speeds or, alternatively, at a selectable one of an innitely variable speed and two or more substantially constant speeds, yet wherein'there is no requirement for auxiliary power take-offs or auxiliary constant speed drive motors.

Consistent with recent technological advances in the field of automation, there has been an ever increasing demand for power machines of the -industrial type whichl are substantially automatic in operation and wherein machine output can be correlated primarily with the speed or capacity of the particular machine rather than primarily with the speed or proficiency of the operator. In the garment or textile industry, this problem has manifested itself in providing industrial-type sewing machines capable of operating at, or approximately at, known constant speeds, thus insuring that maximum productivity is achieved commensurate with the particular pattern of the article being sewn, the particular characteristics of the material being worked upon, and the varying proiciencies of the different machine operators.

One facet of the problem heretofore presented to the manufacturers and users of high-speed, industrial-type sewing machines has been that of providing a sewing machine power transmission which can be quickly and accurately stopped by the operator with the needle either penetrating the work (i.e., the needle down` position) or with the needle withdrawn from the work (i.e., the needle up position). The former, or needle down position, is required when the operator wishes to turn or pivot the' work about the engaged needle so as to permit continued sewing in a different direction. The latter, or needle uplposition, is required when the operator Wishes to remove the work or to make necessary thread adjustments or the like. However, because of the relatively high rates of speed involved with industrial-type sewing machines (e.g., speeds on the order of up to or in excess of 8,000 r.p.m.), it is diicult-indeed, virtually impossible-to apply the brake at that particular instant which will insure that the machine stops in the desired position. To resolve this diticulty, numerous attempts have been made to devise a satisfactoryposition controlling system which insures that the needle will come to rest ina desired position, e.g., the needle down position. Included among these attempts have been various proposals for initially d-ropping the speed of the sewing machine to a relatively slow, generally constant, known speed which permits application of braking power to the driven system components at, or approxi-mately at, the same phase con- 'ditions every time that the machine is stopped. Such proposals have typically involved the use of relatively expensive auxiliary positioning motors, auxiliary power take-offs, or multiple clutching arrangements and 'the like-all systems which generally require gear trains or similar speed reducing units which are noisy, require considerable lubrication, are relatively large and space consuming, and which are diicult to adjust for different lCC specific applications. As a consequence, these machines are generally custom built by the manufacturer to suit a particular need of the user and they are not generally suitable for use in other applications which require different operating speeds.

Another facet of this problem has been the demand in the textile industry for sewing machines Which can'be used in training Iunskilledrpersonnel or which can be used in training skilled personnel in the performance of some new and intricate operation. In either case, it is desirable that the training operation be initiated at a relatively slow, preferably constant, speed and, as the operators proficiency increases, the speed of the machine is also increased. To accomplish this, it has heretofore been the general practice to provide a spec-ial training machine having a multi-speed drive, which permits initial training of the operator under close supervision at a relatively low machine speed. As in the case of the typical needle positioning systems mentioned above, -sewing machine power transmission systems capable of operating at such a relatively low speed have heretofore generally required either a separate slow speed power source or some type of auxiliary drive connection employing a speed reducing gear train or the like. As an alternative to these approaches, it has been necessary to prov-ide some means for varying theinput-output speed ratio of the belted driving connection as, for example, by stopping the machine and actually shifting the drive belt from one pulley to another, or by changing the drive pulley, or by varying the'diameter of the pulley.

However, the former systems-that is, those requiring special slow speed motors, auxiliary power take-offs, or the like--have simply not provided a satisfactory solution to the problem. Primary disadvantages of conventional sewing machines have been their initial high cost, the cost of maintenance thereof, and excessive noise and weight, as well as excessive space required to house the auxiliary slow speed transmission components. Moreover, such transmissions are generally not adjustable without making substanti-al structural revisions. And, of course, where such systems are employed in conjunction with a sew-ing machine of the type employing an electromagnetic clutch and an electromagnetic brake, provision must be made for isolating those components of the system requiring lubrication from the electromagnetic clutch and brake. A

The latter types of systems-i.e., those requiring variation in the belted drive connection-have also failed t0 provide a satisfactory solution to the problem. That i-s,

while these types of systems are adjustable, they either- I tail -to provide the necessary degree of control over the operating speed of the machine (e.g., no provision is made for insuring that the machine can be operated at `a relatively low -constant speed) or .they require a considerable amount of lost or dead time in order to vary or adjust the machines operating speed.

Accordingly, it is a general object of the invention to provide an improved sewing machine power transmission system which overcomes all of the foregoing disadvantages and which is characterized by its simplicity and reliability in operation. More specifically, it is an object of the invention to provide an improved multiple speed sewing machine drive arrangement characterized by its versatility and wherein a single Imachine may be readily used for either :production operations or for training both inexperienced and experienced personnel.

In one of its important aspects, it is an object of the invention to provide an improved method Iand apparatus stant speed, or at a :selectable one of n different constant speeds, irrespective of fluctuations in load or line voltcoupled to any suitable current source (not shown) for effecting energization thereof. As here shown, the motor shaft 36 is adapted to be selectively and disengageably connected to the output shaft 31 `of the transmitter 21 by me'ans of an electromagnetic friction clutch, generally indicated at 38. To this end, the shaft 31 is maintained in axially spaced, coaxial relation with respect to the motor shaft 36, as for example, -by journalling the shaft 31 in spaced antifriction bearings 39 carried by the hub 40 of an end cap 41-the latter being rigidly secured to the housing 22 by means of suitable fasteners 42. The inner end of the shaft 31 (i.e., the left end, or the end adjacent the motor shaft 36 as viewed in FIG. 2) has mounted thereon an externally splined annular 'ring 44 which is keyed to the shaft 31 for simultaneous rotation therewith by means of a suitable key 45. A snap ring 46 and annular spacer 48, the latter being disposed -between the ring 44 and the innermost bearing 39, are utilized to hold Ithe ring 44 in a fixed axial position relative to the shaft 31.

For the purpose of completing a disengageable driving connection, the electromagnetic friction cl-utch 38 includes an internally splined disk 49 of magnetic material which is loosely fitted on the externally splined ring 44, the mating splined arrangement permitting freedom of limited axial viding a rotatable drive connection therebetween. A ring of friction material 50 is secured to the inner face of the disk 49, the friction -material Ibeing confined within the radially spaced annular flanges 51, 52 integral with the disk. The .inner radial surfaces or pole faces ofthe flanges 51, 52 are flush with the inner radial surface of the friction material 50. The arrangement is such that the inner radial faces of the friction material 50 and the flanges 51, 52 are juxtaposed to the outer radial face of a flywheel 54, the latter being non-rotatably secured, as by a key 55, to the motor shaft 36.

In the exemplary construction, the flywheel 54 projects into a tubular flange 56 integral with the end cap 41, there being an annular radial gap 5'8 between the cylindrical telescoped surfaces of the flywheel 54 and the flange 56. A second tubular flange 59, integral with the end cap 41 and having a smaller diameter than the flange 56, projects towards, but terminates short of, the outer radial face of the flywheel 54, the flange 59 being dimensioned to surround the outer peripheral `face ofthe disk 49 and defining therebetween a second radial gap 60. Thus, the end cap 41 with its flanges 56, 59, flywheel 54, and disk 49 with its flanges or pole faces 51, 52 define a toroidal shaped flux circuit 61 including radial gaps 58 and 60, which gaps are sufficiently large in 'area Ito carry the flux required for producing the desired high density between the driving and driven radial faces of the flywheel 54 and the disk 49 and its ring of friction material 50. For creating the flux threading through the circuit 61, a multiple turn annular clutch coil 62 is secured to the end cap 41 -between the flanges 5'6, 59 and within the circuit 61. As a consequence of this construction, when the coil 62 is energized, Ithe flux threading axially through the opposed clutch faces draws the disk 49 into intimate clutched engagement with the driving flywheel 54.

The illustrative power transmitter also includes an electromagnetic friction brake, generally indicated at 64, `having an internally splined disk 65 of magnetic material loosely mounted on the externally splined ring 44 outboard of the clutch disk 49'and adapted to be selectively drawn into intimate frictional :braking engagement with a stationary plate 66 rigidly secured to the end cap 41. The brake disk '65 is formed in a manner similar to the clutch disk 49, here being provided with flanges 68, 69 defining radial pole faces yflush with the outer face of a ring of friction material 70, the latter being confined in the annular channel defined by the flanges 68, 69. The disk 65 is dimensioned so as to define a radial gap 71 between its defined yby the end cap 41 with its flanges 59, 74, brake plate 66, and brake disk 65 with its flanges or pole faces 468, 69, the flux circuit 75 here including radial gap 71. Thus, when the brake coil is energized, the disk 65 is drawn into gripping engagement with the plate 66.

In accordance with one of the important aspects of the present invention, provision is made for automatically breaking the energizing circuit for the clutch coil 62 whenever the speed of the sewing machine 10 exceeds a predetermined selectable value w, and for automatically reestablishing the clutch energizing circuit so as to reenergize the clutch coil 62 w-henever the speed of the sewing .machine drops below the particular speed w that has been selected. To accomplish this, the exemplary sewing machine 10 is provided with a speed controller o'r governor, generally indicated at 76 (FIGS. 1, 2 and 3), having a centrifugally operated make and break switch 78 (best illustrated in FIGS. 3 and 4) adapted to be selectively inserted into the clutch energizing circuit.

Referring to FIGS. 2 and 3 conjointly, it will be noted that the illustrative speed controller 76, includes a housing 79 which is.- rigidly secured to a bracket 80 by shaft 31 (FIG. 2).

any suitable fastening means such, for example, as a threaded fastener 81. While it will become apparent as the ensuing description proceeds that the speed controller d a screw 82 or similar fastener, while the housing 79 is provided with an opening 84 into which projects an outboard shaft extension 31a integral with the clutch shaft,

31. A disk 85 formed of any suitable nonconductive material and having an integral sleeve-like hub insert 86 is' rigidlyV secured by means of set screws 88 or the like to the inwardly projecting end of the shaft extension 31a for simultaneous rotation with the shaft 31.

In the exemplary speed controller 76, the certrifugally operated make and break switch 78 is mounted on one face of the disk 88 and comprises a pair of contacts 89, 90 which are normally engaged or closed when the rotational speed of the disk 88, and hence the speed of all the driven machine components, is equal to or less than the preselected operating speed w. As best shown in FIG. 4, the contacts 89, 90 are mounted on respective different ones of a pair of conductive contact arms 89a, 90a secured to conductive,` leaf springs `91, 92. The latter are carrie-d by brackets 94, which are, in turn, respectively secured to the disk 85 by fasteners 96, 98. The arrangement is such that the fasteners 96, 98 pass completely through the disk 85 and are electrically connected withrespective different ones of a pair of radially spaced, concentric, annular rings 99, 100 (FIG. 3) formed on the opposite face of the disk and positioned to be engaged with different ones of a. pair of stationary wipers W-1, W-Z. The wipers are here supported by lllolsders 102, 104 mounted on a stationary housing plate In carrying out the invention, the innermost contact 89 is held in a fixed position by means of an adjusting link 106 having one end secured to the contact arm 89a and its opposite end secured to an adjusting lever 108 mounted on the face of the disk 85. Thus, theA link 106 prevents movement of the contact 89 due to centrifugal forces during rotation of the disk 85. However, the outermost contact 90 is free to move outwardly-ie., away from contact 89-to a limited extent whenever the speed of the disk 85 reaches a value such that the centrifugal forces present are sufficient to overcome the biasing effect of spring arm 92 and a biasing spring 109, the latter having one end secured to the arm 90a and its opposite end abutting a stop lug 110 integral with the disk 85.

In order to facilitate an understanding of the operation of the exemplary speed controllerv 76, reference is here made to FIG. wherein certain of the elements described above are depicted in schematic form. As here shown, it will be observed that the conductive ring 100 is coupled by means of the wiper W-Z directly to one terminal L-1 of a suitable D.C. source (not shown), while the ring 99 is electrically coupled through the wiper W-l to the clutch coil 62 and thence to the other terminal L-2 of the D.C. source. As long as the speed of the disk 85 remains equal to or below a preselected speed w, the con tacts 89, 90 remain closed and an energizing circuit for the clutch coil 62 is completed from the terminal L-l, through Wiper W-2, ring 100 leaf spring 92 (including spring bracket 95 and fasteners 98-FIGS. 3 and 4), contacts 89, 90, spring 91 (including spring bracket 94 and fasteners 96-FIGS. 3 and 4), ring 99, wiper W-1, and coil 62, back to the terminal L-2. However, when the speed of the disk 85 exceeds the preselected. speed w, the contacts S9, 90 open due to shifting of the contact 90 under the centrifugal forces present in the system, thus breaking the energizing circuit for the clutch coil 62 and permitting the disk 85 to slow down. As soon as the speed of the disk again drops below the preselected speed w, the contacts 89, 90 reclose and the coil 62 is again energized. Those skilled in the art will appreciate from the foregoing that the contacts 89 and 90 will rapidly and continuously make and break on a periodic basis so as to insure that the disk 85 (and hence all other driven system components) is driven at a substantially constant preselected speed w irrespective of variations in the driven load or fluctuations in line voltage.

In order to provide close, accurate, smooth control over the regulated operating speed permitted by the exemplary speed controller 76, a resistor R-1 may be connected across the contacts 89, 90 thus insuringv that when the contacts are closed, a maximum voltage (here, lline voltage) is applied to the clutch coil 62 and, when the contacts 89, 90 are open, a lesser voltage is applied across the clutch coil 62 lbecause of the voltage drop across the series resistor R-1 which is introduced into the clutch energizing circuit. By proper selection of a resistor R-l having suitable characteristics, it is, therefore, possible to insure that the sewing machine will run smoothly at any particular speed for any given set of load. conditions. A capacitor C-1 is preferably connected across the contacts `89, 90 for the purpose of absorbing the decay transient of the clutch coil 62 when the energizing circuit for the latter is interrupted.

In keeping with one of the important objectives of the invention, means are provided for permitting adjustment of the preselected operating speed w, so as to permit production operations under optimum speed conditions commensurate with the particular job being performed or, in a training operation, to permit adjustment of machine speed as the operator-trainees proficiency increases. In the illustrative device, this is accomplished by varying the biasing effect of the springs 92, 109, for example, by shifting the contact 89 inwardly, thus varying the centrifugal force required to open the contacts. To this end, the adjusting lever 108 is pivoted at 111 toa bracket 112 integral with the disk 85, the lever being provided with a tang 114 to which is secured the adjusting link 106. The lever 108 further includes a radially extending arm 115 having an actuating Abutton 116 formed on its inner end coaxial with the axis of rotation of the disk 85.

The arrangement is such that any suitable manually adjustable device (such, merely `by way of example, as the threaded control knob and plunger assembly 118 shown in FIG. 3) can be utilized to convert rotary motion of a control knob 119 to linear axial motion of an actuating plunger 120, the latter being adapted to engage and shift the button 116 in an axial direction. Shifting of the 'button 116 inwardly (i.e., to the left as viewed in FIG. 3) serves to pivot the lever 108 in a counterclockwise direction about its pivot point 111, thus causing the junction point between the link 106 and the tang 114 to move in a clockwise direction (i.e., along the path described by arrow P in FIG. 3) and shifting the link 106 downwardly. As the link 106 moves, the contact arm 89a and contact 89 are shifted downwardly, or away from the stop lug 110, thus decreasing the biasing force cre- -ated by springs 109 and 92 which tends to hold the contacts 89, 90 closed, and reducing the centrifugal forces required to open the contacts.

The overall operation of the exemplary power transmission system and electrical control circuits `associated with the form of the invention shown in FIGS. l-4 will here be described in detail in conjunction withthe schematic wiring diagram shown by way of example in FIG. 7.

In order to prepare or condition the sewing machine 10 foran operating cycle, the operator first turns the ON- OFF switch 121 (FIGS. l and 7) to the ON state, thus coupling the terminals L-l, L-2 of a suitable A.C. source (not shown) directly to the motor (FIGS. 2 and 7) and to the power supply for the brake coil 72 and the clutch control circuit 122. At this time, the foot treadle 124 associated with a foot controller, generally indicated at 12S in FIGS.1 and 7, is heeledj thus closing the normally open contacts TS1 controlled by a treadle switch (not shown) disposed beneath the treadle 124 and completing an energizing circuit for the brake coil 72. The motor 35 is now running, the clutch coil 62 is deenergized,

. and the brake coil 72 is energized. The sewing machine 10 is now in readiness for anoperating cycle.

In the exemplary circuit, the terminals L-1, L-2 of the A.C. source are coupled to the primary winding w1 of a transformer T1 having a secondary winding W2. As here shown, the secondary winding W2 provides a source of voltage for the brake and clutch coils through 4a voltage doubler 126 including diodes D1, D2 and capacitors C2, C3. Referring to FIG. 7, it will be observed that the voltage source for the brake coil 72 is derived from the terminals t1, t2 of the voltage doubler 126. As a consequence of this construction, at the instant the brake is energized, a maximum voltage, for example, approximately 300 volts, is applied across the terminals of the brake coil 72 through the contacts TS1 and a capacitor C4. However, when the capacitor C4 charges, the energizing circuit for the coil 72 is completed through a current limiting resistor R2 which serves to drop the voltage supplied to the coil 72 to its standard rated capacity, for example, approximately volts. In the energizing circuit for the clutch coil 62, on the other hand, the voltage is derived from the terminals t2, t3 of the voltage doubler 126-that is, across the terminals of only the capacitor C3 which acts as a lter to smooth the pulsating voltages applied to the coil. Thus, the clutch coil s energized at a considerably lower voltage level than the brake coil, a level which, for example, may be approximately 60 volts under high-speed operating conditions and a lesser voltage level at lower selected operating speeds.

Assuming that the operator desires to run the sewing machine 10 at a constant slow speed (as compared to its constant high speed when full line voltage across the terminals t2, t3 is continuously applied across the clutch coil 62), it is Simp-ly necessary that the treadle 124 associated with the operator actuated foot controller 125 be toed or depressed slightly. This serves to open the contacts TS1 in the brake energizing circuit, thus deenergizing the brake coil 72 and permitting transmission of power from the motor 35 to the clutch shaft 31. At the same time, slight toeing or depression of the treadle 124 serves to shift the speed selector wiper W-3 of the foot controller 125 into engagement with a slow speed terminal SS of the latter, thus coupling the terminal t3 of the voltage doubler 126 to the clutch coil 62 through the speed controller 76 and a variable resistor R3. This completes an energizing circuit for the clutch coil 62 through the speed controller 76 which functions in the manner described above to regulate the speed of the clutch shaft 31 and maintain the latter at a substantially constant speed w. Thus, when the contacts 89, 90 are closed (i.e., when the speed of the disk 85 is equal to or less thanw), the full -line voltage (less the voltage drop across variable resistor R3) derived from the terminalslZ, t3 of the voltage doubler 126 is applied across the clutch coil. When the speed of the disk 85 exceeds w, the centrifugal forces developed will cause the contacts 89, 90 to open or break, thus completing the energizing circuit for the clutch coil 62 through the current limiting resistor R1 and the variable resistor' R3. The voltage drop across the former is sufficient to cause the sewing machine 10 to again drop to a speed at, or slightly below, w, whereupon the contacts 89, 90 reclose. Periodic opening and closing of the contacts 89, 90 will, in the foregoing manner, maintain the sewing machine speed substantially constant at the selected speed W. And, of course, this speed w may be readily adjusted within a relatively wide range by the simple expedient of turning the control knob 119 of the manually operable speed adjuster 118 (FIG. 3).

In keeping with the invention, provision is also made for insuring that the regulated speed w of the sewing machine 10 remains substantially constant irrespective of minor deviations in the position of the treadle 124 occasioned by inadvertent changes in the pressure exerted thereon by the operators foot. To this end, the speed selector wiper W-3 and the slow speed terminal SS of the foot controller define a sector contact which will remain closed irrespective of minor changes in treadle position. While the illustrative sector contact is here shown as comprising a slow speed terminal SS having an arcuate configuration,

those skilled in the art will appreciate that the foot controller 125 could take other forms and still fall within the scope of the invention. Merely by way of example, the speed selector wiper W-3 could have a cam surface formed thereon adapted to slidably engage =a slow speed terminal SS defining a point contact. In either case, the wiper and slow speed Vterminal define a sector contact which permits ofminor deviations in treadle position without disrupting operation of the speed controller 76.

While a sewing machine 10 embodying a speed controller 76 of the foregoing character will find particularly advantageous application in either training operations or in production operations wherein Vit is desirable to maintain the operating speed of the machine at a relatively slow constantspeed level w, it is often desirable that the same machine be operated at a dilerent and faster substantially constant speed wf. To permit operation of the sewing machine at such a faster speed, the exemplary foot controller 125 includes a high-speed terminal HS which is coupled directly to the clutch coil 62 through the variable resistor R3. The arrangement is such that when the operator desires to run the sewing machine at -a substantially constant, relatively high speed wf, it is simply necessary to toe or depress the foot treadle 124 fully, thus shifting the wiper W-3 into engagement with the highspeed terminal HS and effectively bypassing the slowspeed regulator or controller 76. In this mode of operation, the voltage applied across the clutch coil 62 will be the line voltage derived from the terminals t2, t3 of the voltage doubler 126 (less any voltage drop across variable resistor R3) and the machine 10 will, therefore, run at a high rate of speed wf Which will remain substantially constant except for changes in line voltage and changes in loading conditions.

Upon completion of an operating cycle at either the low constant speed w or the high constant speed wf, it is simply necessary to heel the treadle 124 in a convent-ional manner so as to effect stopping of the sewing machine. Thus when the treadle is heeled, the wiper W-T moves to a position spaced from both the highspeed terminal HS and the slow-speed terminal SS, thereby deenergizing the clutch coil 62 and breaking the drive connection between the motor shaft 36 and the clutch shaft 31. At the same time, heeling of the treadle 124 closes the contacts TS1 of the treadle switch, thus completing an energizing c-ircuit for the brake coil.

In order to further enhance the versatility of sewing machines embodying the features of the present invention, provision may be made for permitting selective operation ,of the sewing machine 10 at either a substantially constant lslow speed w, a substantially constant fast speed wf, or at any desired speed infinitely variable between fixed upper and lower limits. 4To this end, there is illustrated in FIG. 8 a slightly modiied sewing machine power transmission system also embodying the features of the present invention. In view of the similarities in the two illustrative systems, like parts in both systems will .be designated by identical reference numerals, and those parts not common to the two systems will be designatedby different reference numerals.

It will be observed upon comparison of the illustrative circuits `shown in FIGS. 7 and 8, that provision is made in both systems for permitting selective operation of the sewing machine at either a substantially constant slow speed w (i.e., when the wiper W-S is engaged with the terminal SS) or at a substantially constant high speed wf (i.e., When the Wiper W-3 is engaged with the terminal HS). However, in the exemplary system shown in FIG. 8, a modied type of foot controller 12S is provided Which incorporates not only a slow-speed terminal SS and a high-speed terminal HS, but, in addition, includes an operator controlled rheostat 128 which permits of operation at a selectable variable speed wv determined by the position of the wiper W-S which here constitutes the wiper of the rheostat 128. In this instance, slight toeing7 or depression of the treadle 124 completes a slow speed energizing circuit for the clutch coil 62 through the speed controller 76 by virtue of closure of the sector contact W-3, SS. If high .speed operation is desired, the treadle 124 is fully toed so as to shift the wiper W-3 to the high speed terminal HS. l

However, where the particular job being performed by the operator requires operation at numerous dilierent speeds, the treadle 124 is toed sufficiently to shift the wiper W-3 past the terminal SS and into engagement -with the resistor R4 'which forms part of the `rheostat 128. In this condition, vari-ations in the position of the treadle 124 under control of the operators foot will effectively vary the total resistance in the energizing circuit for the clutch coil 62, thus permitting energization of the latter at -a selectable one of an infinitely variable number of different voltage levels and causing operation of the sewing mach-incl() at la speed wv dependent upon the extent of the magnetic coupling between the driving and driven clutch elements 54, 49 (i.e., as the treadle 124 is progressively toed through greater angular increments, the resistance in the clutch energizing circuit is progressively decreased, thereby progressively increasing the energizing voltage for the coil 62 and thus the magnetic coupling between the clutch elements 49, 54).

Turning next to FIGS. 6 and 9, there is shown a slightly modified power transmission system similar to the system shown in FIGS. 1-5 and 7, but which here permits of selective machine operation at any one of n different const-ant speeds (n here being equal to four different speeds). Again, because of the similarities in the two systems, like parts in both systems will be designatedby similar reference numerals and those parts not common to the two systems will be designated by different reference numerals.

As best shown in' FIG. 6, three substantially identical speed controllers 76, '76 and 76 respectively having hub inserts 86, 86 and S6"are rigedly secured by means of fasteners 8S in axially spaced relation upon a hollow tubular shaft 129 integral with the clutch shaft extension 31a. The specific structural details of each of the three spaced controllers 76, 76 and 76 are identical to that previously described in connection with FIGS. 3 and 4 and, therefore, will not be furthe-r detailed here. It should suffice to point out that the three sets of make and break contacts 39-90, SQLQ and 89"-96 are here set to break due to centrifugal forces at three different constant slow speed settings w, w and w, and this can be achieved either by selective and independent manual adjustment of the adjusting levers 106, 106 and 106 or, alternatively, by varying the design characteristics of the springs, contacts and contact arms of the different controllers 76, 76', 76".

To permit independent manual adjustment of the speed settings for the three controllers 76, 76 and 76", cach is provided with an actuating button (buttons 116g, 116 and 116 respectively) similar to the button 116 shown in FIG. 3, the buttons being coaxially spaced with buttons 116', 116 disposed within sleeve 129. To permit axial shifting of the buttons 116' and 116, the latter are mounted on the innermost ends of arms 115', 115" respectively associated with adjusting levers 168', MSL-the arms 115', 115" respectively passing through elongate slots 130, 131 formed in the tubular shaft 129. In this instance, the button 11601 is annular in configuration and is shifted axially by means of any suitable type of axially 'shiftable tubular plunger 12th:. In like manner, the button 116' is also annular and is shifted axially by means of an independently adjustable tubular actuating plunge-r 120 which passes through the plunger 126g and button 11661 with freedom for sliding movement relative thereto. The button 116 is adjusted axially by means of a sepa; rate actuating plunger 120 passing through the plungers 120e, 120 and the buttons 116a, 116 with freedomfor sliding movement relative thereto. The particular means employed for shifting the plungers 126m, 120 and 126 axially is not critical to the present invention and may be similar to the adjusting assembly 118 shown in FIG. 3 or, alternatively, may tak-e any other form well known to those skilled in the art.

The foregoing arrangement is such that the three speed controllers 76, 76 and 76" serve to maintain the operating lspeed of the sewing machine 1li at a selectable one of three different constant speed settings wjw', oir w dependent upon which of the three controllers is selected, and each speed setting is independently adjustable. Of course, those skilled in the art will appreciate that the speed cont-rollers 76, 76 and 76 could be disposed in other than coaxial relation. Moreover, there could be more or fewer than the illustrative three speed controllers dependent upon the particular requirements of the user.

Turning next to FIG. 9, it will be observed that the three speed controllers 76, 76' and 76 shown in FIG. 6 are here electrically connected to respective different ones of three slow speed terminals SS, SS' and SS" disposed within a modified foot cont-roller 125 similar to the controller 125 shown in FIGS. l and 7. In this instance, the speed controllers 76, 76 and 76 may be selectively inserted into the energizing circuit for the clutch coil 62 one at a time by the simple expedient of toeing the treadle 124 a sufficient amount to close a selectable one of the three sets of sector contacts W-3, SS; W-3, SS; or W-3, SS. Alternatively, all three of the speed controllers may be bypassed by toeing the treadle 124 so as to shift the wiper W-3 to a position engaging the high speed terminal HS in the foot controller 125.

It will be appreciated from the foregoing that a power transmission system embodying the features of the present invention will be characterized by its simplicity, effectiveness, and reliability in operation. The provision of n centrifugal speed cont-rollers (where n can be equal t0 1, or any desired multiple thereof) of the type which permit accurate control of the energizing voltages applied to the clutch coil in a sewing machine electromagnetic clutch, insures that the sewing machine can be operated at a selectable one of n-j-l different speeds, all of which are maintained relatively constant with a high degree of accuracy, and wherein the ni relatively slow speeds are maintained substantially constant irrespective of variations in load andline voltage. At the same time, the requirement for heavy, bulky, and expensive auxiliary drive motors and auxiliary power take-offs which require speed reducing gear trains, together with their lubrication and other inherent servicing problems attendant such devices, is eliminated, thereby providing a quiet, compact, lightweight, sewing machine power transmission which is relatively inexpensive and maintenance free.

I claim as my invention:

1. In combination with a sewing machine of the type having a reciprocable needle operatively connected to and driven by a clutch shaft, a power transmission system for driving said machine at a predetermined speed and comprising a power source including a drive shaft, a drive element secured to said drive shaft, a driven element secured to said clutch shaft, and electromagnetic means including a coil for establishing a flux circuit threading through said drive and driven elements whereby a driving connection is established between said elements when said coil is energized so as to transmit power from said power source to said needle, a voltage source for energizing said coil, and means coupling said coil t0 said voltage source, said coupling means including a speed responsive centrifugally actuated switch device for reducing the voltage supplied to said coil whenever the speed of said machine exceeds said predetermined speed and for increasing the voltage supplied to said coil when the speed of said machine drops to said predetermined speed whereby said machine is driven at said predetermined speed.

2. In combination with a sewing machine of the type having a reciprocable needle operatively connected to and driven by a clutch shaft, a power transmission system for driving said machine at a predetermined speed and comprising a power source including a drive shaft, a drive element secured to said drive shaft, a driven element secured to said clutch shaft, and electromagnetic means including a coil for establishing a ux circuit threading through said drive and driven elements whereby a driving connection is established between `said elements when said coil is energized so as to transmit power from said power source to said needle, a voltage source for energizing said coil, and a speed controller coupled to and driven by said clutch shaft, said controller including first and second contacts connected to respective different ones of said coil and said voltage source, means biasing one of said contacts into engagement with the other of said contacts so that said contacts are closed when the clutch shaft is driven at speeds less than said predetermined speed to complete an energizing circuit for said coil and so that when the speed of the clutch shaft exceeds said predetermined speed the centrifugal forces developed overcome said biasing means whereupon said one Contact moves away from the other of said contacts to interrupt the energizing circuit for said coil.

3. In combination witha sewing machine of the type having a reciprocable needle operatively connected to and driven by a clutch shaft, a power transmission system for driving said machine at a predetermined speed and comprising a power source including a drive shaft, a drive element secured to said drive shaft, a driven element secured to said clutch shaft, and electromagnetic means including a coil for establishing a flux circuit threading through said drive and driven elements whereby a driving connection is established between said elements when said coil is energized so as to transmit power from said power source to said needle, a voltage source for energizing said coil, a centrifugally operated make and break switch coupled to and driven by said clutch shaft,

13 said switch having terminals connected to respective ones of said voltage source and said coil for completing an energizing circuit for the latter when said switch is closed, and means for urging said switch to its closed state at all speeds less than said predetermined speed, said last named i. driving said machine at a selectable and variable predetermined speed and comprising a power source including a drive shaft, a drive element secured to said drive shaft, a driven element secured to said clutch shaft, and electromagnetic means including a coil for establishing a ux circuit threading through said drive and driven elements whereby a driving connection is established between said elements when said coil is energized' so as to transmit power from said power source t`o said needle, a voltage source for energizing said coil, a centrifugally operated make and break switch coupled to and driven by said clutch shaft, said switch having terminals connected to respective ones of said voltage source and said coil for completing an energizing circuit for the latter when said switch is closed, biasing means for urging said switch to its closed state at allspeeds less than said predetermined speed, said last named means being insuicient to overcome the centrifugal force developed at speeds in excess of said predetermined speed whereupon said switch is centrifugally shifted to its open state to interrupt the energizing circuit for said coil, and means for selectively varying the predetermined speed at which said switch opens, said last named means including means for varying the biasing elfect of said biasing means so as to vary the centrifugal force required t shift said switch to its open state.

5. In combination with a sewing machine of the type having a reciprocable needle operatively connected to and driven by a clutch shaft, a power transmission system for driving said machine at a predetermined speed and cornprising a power source including a drive shaft, a drive element secured to said drive shaft, a driven element secured to said clutch shaft, and electromagnetic means including a coil for establishing a flux circuit threading through said drive and driven elements whereby a driving connection is established between said elements when said coil is energized so as to transmit power from said power source to said needle, a voltage source for energizing said coil, a centrifugally operated make and break switch coupled to and driven by said clutch shaft, said switch having terminals connected to respective ones of said voltage source and said coil for completing an energizing circuit for the latter when said switch is closed, means for urging said switch to its closed state at all speeds less than said predetermined speed, said last named means being insufficient to overcome the centrifugal force developed at speeds in excess of said predetermined speed whereupon said switch is centrifugally shifted to its open state to interrupt the energizing circuit for said coil, and means coupling said voltage source to said coil for supplying a reduced voltage to the latter when said switch is open.

6. In combination with a sewing machine of the type having a reciprocable needle operatively connected to and driven by a clutch shaft, a power transmission system for driving said machine at a substantially constant predetermined speed and comprising a power source including a drive shaft, a drive element secured to said drive shaft, a driven element secured to said clutch shaft, said drive and driven elements being supported to move together and form a friction drive connection therebetween, and electromagnetic means including a coil for establishing a flux circuit threading through said drive and driven elements 1li to move the same together whereby a driving connection is established between said elements when said coil is energized so as to transmit power from said power source to said needle, a voltage source for energizing said coil,

iirst and second energizing circuits connecting said coil and said voltage source for respectively energizing said coil at first and second voltage levels suliicient to drive said clutch shaft at iirstand second speeds above and below said predetermined speed, and means for alternately energizing saidcoil through said lirst and second circuits on a rapid periodic basis as the speed of said clutch shaft Y falls below or rises above said predetermined speed so that said 4machine is driven at said substantially constant predetermined speed between said iirst and second speeds.

7. In combination with a sewing machine of the type having a reciprocable needle operatively connected to and driven by a clutch shaft, a power transmission system for driving said machine at a selectable one of n constant speeds comprising, a power source including a drive shaft,

a drive element secured to said drive shaft, a driven element secured to said clutch shaft, said drive and driven elements being supported to move together and form a friction drive connection therebetween, electromagnetic means including a coil for establishing a flux circuit threading through said drive and driven elements to move the same together whereby a driving connection is established between said elements when said coil is energized, a voltage source for energizing said coil, n speed responsive devices respectively corresponding to said n constant speeds for selectively coupling said voltage source to said coil to energize the latter, each of said n speed responsive devices being normally disconnected from one of said coil and said voltage source, selector meansfor coupling said voltage source to said clutch coil through a selected one of said n speed responsive devices, said selected device adapted to reduce the voltage supplied to said coil from said voltage source whenever the speed of said machine exceeds the one of said n constant speeds corresponding to the selected one of said n devices and to increase the volta-ge supplied to said coil when the speed of said machine drops to said one of said n constant speeds whereby said machine is driven at said selected one of said n constant speeds.

8. In combination with a sewing machine o f the type having a reciprocable needle operatively connected to and driven by va clutch shaft, a power transmission system for driving said machine at a selectable one of an infinitely variable speed and n constant speeds comprising, a power source including a drive shaft, a drive element secured to said drive shaft,'a driven element secured to said clutch shaft, said drive and driven elements being supported to be moved together to form a friction drive connection therebetween, electromagnetic means including a coil for establishing a flux circuit threading through said drive and driven elements to move the same together whereby a driving connection is established between said elements when said coil is energized, a voltage source for energizing said coil, n speed responsive devices respectively corresponding to said n constant speeds for selectively coupling said voltage source to said coil to energize the latter, selectively operable means coupling said voltage source to said coil for energizing the latter at a selectable and infinitely variable level, each of said n speed responsive devices and said selectively operable means being normally disconnected from one of said coil and said voltage source, selector means for coupling said voltage source to said clutch coil through a selected lone of said n speed responsive devices and said selectively operable means, said deviceseach adapted upon selection to reduce the voltage supplied to said coil from said voltage source whenever the speed of said machine exceeds the one of said n constant speeds'corresponding to the selected one of said n devices and to increase the voltage supplied to said coil when the speed of said machine drops to said one of said n constant speeds whereby said machine is driven at said selected one of said n constant speeds, and said selectively operable means being effective upon activation by said selector means to provide a selectable and infinitely variable voltage to said coil for energizing the latter at a selectable level determined by the position of said selector means.

9. In combination with a sewing machine of the type having a reciprocable needle operatively connected to and driven by a clutch shaft, a power transmission system for driving said machine at a selectable one of at least three different substantially constant speeds comprising,

a power source including a drive shaft, a drive elementv secured to said drive shaft, a driven element secured to said clutch shaft, said drive and driven elements being supported to move together to form a friction drive connection therebetween, electromagnetic means including a coil for establishing a flux circuit threading through said drive and driven elements to move the same together whereby a drivin-g connection is established between said elements when said coil is energized, a voltage source for energizing said coil, at least two speed responsive devices respectively corresponding to at least two of said constant speeds for selectively coupling said voltage source to said coil to energize the latter, means defining a high speed circuit for selectively coupling said voltage source to said coil to energize the latter, each of said speed responsive devices and said high speed circuit being normally disconnected from one of said coil and said voltage source, operator controlled selector means for coupling said voltage source to said clutch coil through a selected one of said speed responsive devices and said high speed circuit, said devices each adapted upon selection by said selector means to reduce the voltage lsupplied to said coil from said voltage source whenever the speed of said machine exceeds the one of said constant speeds corresponding to the selected one of said devices and to increase the voltage supplied to said coil when the speed of said machine drops to said one of said constant speeds whereby said machine is driven at said selected one of said constant speeds, and said high speed circuit being adapted upon selection by said selector means to supply a maximum voltage to said coil whereby said machine is driven at the highest of said substantially constant speeds.

10. In combination with a sewing machine of the type having a reciprocable needle operatively connected to and driven by a clutch shaft, a power transmission system for driving said machine at a selectable one of a first predetermined substantially constant speed w and a second speed comprising, a power source including a drive shaft, a drive element secured to said drive shaft, a driven element secured to said clutch shaft, said drive and driven elements being supported to move together to form a friction drive connection therebetween, electromagnetic means including a coil for establishing a flux circuit threading through said drive and driven elements to move the same together whereby a driving connection is established between said elements when said coil is energized, a voltage source for energizing said coil, first and second coupling means normally disconnected from one of said voltage source and said coil for selectively coupling said voltage source to said coil to energize the latter, and selector means for coupling said voltage source to said coil through a selectable one of said first and second coupling means, said first coupling means including a speed responsive device for reducing the voltage supplied to said coil by said voltage source whenever the speed of said machine exceeds w and for increasing the voltage supplied to said coil when the speed of said machine drops to said constant speed w whereby said machine is driven at said first predetermined substantially constant speed w upon selection of said first coupling means and at said second speed upon selection of said second coupling means.

11. The co-mbination set forth in claim 10 further characterized in that said second coupling means includes a high speed terminal coupled directly to one of said Voltage source and said coil so that upon operation of said selector means to effect selection of said second coupling means said voltage source is directly coupled to said coil to effect maximum energization thereof and said machine is driven at a maximum, substantially constant speed.

12. The combination set forth in claim further characterized in that said selector means is operator controlled, and said second coupling means defines with said selector means a rheostat connection so that upon operation of said selector means to effect selection of said second coupling means said machine is driven at a selectable and infinitely variable speed in accordance with the selected condition of said rheostat connection.

13. The combination set forth in claim 10 further characterized in that said second coupling means includes a speed responsive device for reducing the voltage supplied to said coil by said voltage source whenever the 20 speed of said machine exceeds said second speed and for increasing the voltage supplied to said coil when the speed of said machine drops to said second speed so that upon selection of said second coupling means by operation of said selector means said machine is driven at a substantially1 constant rate of speed correspondingto said second spee 14. In combination with a sewing machine of the type having a reciprocable needle operatively connected to and driven by a clutch shaft, a power transmission system for driving said machine at a selectable one of a first predetermined substantially constant speed w and a second speed comprising, a power source including a drive shaft, a drive element secured to said drive shaft, a driven element secured to said clutch shaft, said drive and driven elements being supported to move together to form a friction drive connection therebetween, electromagnetic means including a coil for establishing a flux circuit threading through said drive and driven elements to move the same together with a force proportional to the energization of said coil whereby a driving connection is established between said elements when said coil is energized, a voltage source for energizing said coil, first and second coupling means normally disconnected from one of said voltage source and said coil for selectively coupling said voltage source to said coil to energize the latter, and operator'controlled selector means for coupling said voltage source to said coil through a selectable one of said first and second coupling means, said operator controlled selector means defining at least one sector contact so that minor deviations in the position of said selector means are ineffective to interrupt the voltage supplied to said coil by said source, said first coupling means including a speed responsive device for reducing the voltage supplied to said coil by said voltage source whenever the speed of said machine exceeds w and for increasing the voltage supplied to said coil Cat when the speed of said machine drops to said constant speed w whereby said machine is driven at said first predetermined substantially constant speed w upon selection of said first coupling means and at said second speed upon selection of said second coupling means.

References Cited by the Examiner UNITED STATES PATENTS 1,994,626 3/1935 Townsend 318--325 G5 2,246,803 6/1941 Lee 318-325 2,281,711 5/1942 Peck et al B18-325 2,337,066 12/1943 Schmitt et al 112-220 2,420,346 5/1947 Anderson 318-325 X 2,920,221 1/1960 Schwab 112-219 FRANK I. COHEN, Primary Examiner.

ROBERT V. SLOAN, Examiner. 

1. IN COMBINATION WITH A SEWING MACHINE OF THE TYPE HAVING A RECIPROCABLE NEEDLE OPERATIVELY CONNECTED TO AND DRIVEN BY A CLUTCH SHAFT, A POWER TRANSMISSION SYSTEM FOR DRIVING SAID MACHINE AT A PREDETERMINED SPEED AND COMPRISING A POWER SOURCE INCLUDING A DRIVE SHAFT, A DRIVE ELEMENT SECURED TO SAID DRIVE SHAFT, A DRIVEN ELEMENT SECURED TO SAID CLUTCH SHAFT, AND ELECTROMAGNETIC MEANS INCLUDING A COIL FOR ESTABLISHING A FLUX CIRCUIT THREADING THROUGH SAID DRIVE AND DRIVEN ELEMENTS WHEREBY A DRIVING CONNECTION IS ESTABLISHED BETWEEN SAID ELEMENTS WHEN SAID COIL IS ENERGIZED SO AS TO TRANSMIT POWER FROM SAID POWER SOURCE TO SAID NEEDLE, A VOLTAGE SOURCE FOR ENERGIZING SAID COIL, AND MEANS COUPLING SAID COIL TO SAID VOLTAGE SOURCE, SAID COUPLING MEANS INCLUDING A SPEED RESPONSIVE CENTRIFUGALLY ACTUATED SWITCH DEVICE FOR REDUCING THE VOLTAGE SUPPLIED TO SAID COIL WHENEVR THE SPEED OF SAID MACHINE EXCEEDS SAID PREDETERMINED SPEED AND FOR INCREASING THE VOLTAGE SUPPLIED TO SAID COIL WHEN THE SPEED OF SAID MACHINE DROPS TO SAID PREDETERMINED SPEED WHEREBY SAID MACHINE IS DRIVEN AT SAID PEDETERMINED SPEED. 